Search

Currently, efficient and cost-effective recycling of waste capacitors is a pressing issue. In this study, the recovery of electrode powder from waste supercapacitors and enabling the reuse of the prepared samples are reported. The recovered powder is directly activated by mixing it with KOH using chemical activation to regenerate the waste-activated carbon. The regenerated activated carbon's specific surface area could be restored to a level similar to that of the original commercial powder, reaching 1803.15 m2/g. The regenerated activated carbon has a high proportion of microporous, which played a crucial role in its electrochemical performance. The samples' capacity in the organic system reached 125.96 F/g at 0.2 A/g and 111.77 F/g at 20 A/g, with a retention rate of 88.74%. Furthermore, the capacitance was maintained at 91.18% after 10,000 cycles, showing good cycling performance. Additionally, the supercapacitor assembled from the regenerated activated carbon delivered a high energy density of 31.83 Wh/kg and a power density of 269.76 W/kg, indicating great application potential. Overall, this study offers a useful and low-cost approach for recycling activated carbon from waste electrodes, which would be possible for supercapacitors recycling. [Display omitted] • The waste electrode carbon powder is regenerated into activated carbon. • The electrochemical properties of 21RAC-3 are superior than 21KSN. • 21RAC-3 organic supercapacitor exhibits an energy density of 31.83 Wh/kg. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fungal hypha activated carbon pad (FhACPad) is a promising electrode for desalination. • FhACPad is a freestanding electrode readily prepared from the fungus suspension for CDI. • The continuous and porous structure of FhACPad facilitates both electron and ion transfer. • FhACPad with hierarchical pores exhibits a high desalination capacity of 35.6 mg NaCl /g. Capacitive deionization (CDI) is an emerging technology for water desalination, especially low-salinity water. Freestanding porous carbon-based electrodes with rapid electron transfer rate and effective ion diffusion features are desired to achieve high desalination performance. Here, a porous carbon pad derived from the fungal hyphae of Aspergillus niger was prepared as a precursor of the electrode. After carbonization and activation, the intertwined and hierarchical porous structure of the fungal hypha pad was well-preserved, producing a freestanding fungal hypha activated carbon pad (FhACPad) electrode for MCDI. The interconnected carbon fibers and open pore structure of the FhACPad yielded an electrode with high electrical conductivity and rapid ion transport properties. The novel FhACPad exhibited a gravimetric salt adsorption capacity of 35.6 ± 2.3 mg NaCl /g with an average desalination rate of 1.2 mg NaCl /g electrode /min from a 585 mg/L NaCl aqueous solution at a cell voltage of 1.2 V and a flow rate of 1 mL/min. As a result, the FhACPad outperformed conventional powdered activated carbon (PAC) electrodes and the most recently reported porous carbon electrodes under similar desalination conditions. This work also provides insights into the structure-performance relationships of CDI electrodes and shows a great potential of fungal biomass-derived porous carbon electrodes for high-performance MCDI applications. [ABSTRACT FROM AUTHOR]

Conversion of carbon-containing biomass into useful carbon products is highly demanded. A rising understanding of environmental problems explains the growing focus on evaluating bioproducts and wastes in numerous applications. Herein, the wheat husks derived activated carbon (WHAC) was employed as electrode material for supercapacitors' energy storage. Three samples of activated carbon were made using wheat husks, which were activated at different temperatures. The prepared electrodes were characterized and electrochemically tested using Fourier-transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscope, cyclic voltammetry, galvanostatic charge-discharge, and electrical impedance spectroscopy. The maximum capacitance (271.5 F g−1 at a current density of 0.5 A g−1) was observed for AC-800, activated at 800 °C. The electrochemical impedance showed low resistance (3.659 Ω) and low-frequency response (6.84 s). The AC-800 electrode exhibited the capacitance retention of 82% after 5000 cycles. The excellent electrochemical properties reveal the utilization of biomass waste as a potential electrode material for supercapacitors. The process used is simple, environmentally friendly, and could significantly reduce the county's biomass wastes from wheat husks. The approach can not only reduce environmental pollution but develop porous carbon electrodes for energy storage devices. Image 1 • The wheat husks derived activated carbon was prepared on Ni foam substrate. • The activated carbon was chemically activated by impregnating KOH. • The optimum activation temperature was found to be 800 °C. • The electrode showed a high specific capacitance of 271.5 F/g. • The electrode exhibited high energy, power density and cyclic stability. [ABSTRACT FROM AUTHOR]

The development of efficient energy storage systems is critical in the transition towards sustainable energy solutions. In this context, the present work investigates the viability of using orange juice, as a promising and sustainable precursor, for the synthesis of activated carbon electrodes for supercapacitor technologies. Through the carbonization-activation process and controlling the preparation parameters (KOH ratio and activation time), we have tailored the specific surface area (SSA) and pore size distribution (PSD) of the resulting carbon materials—crucial parameters that support supercapacitive performance. Several spectroscopic, morphological, and electrochemical techniques are used to characterize the obtained carbon materials. In particular, our optimization efforts revealed that a 5:1 KOH ratio with an activation time up to 120 min produced the highest SSA of about 2203 m2/g. Employing these optimal conditions, we fabricated symmetric coin cell supercapacitors using Na2SO4 as the electrolyte, which exhibited interesting specific capacitance (~56 F/g). Durability testing over 5000 cycles sustained the durability of the as-made activated carbon electrodes, suggesting an excellent retention of specific capacitance. This study not only advances the field of energy storage by introducing a renewable material for electrode fabrication but also contributes to the broader goal of waste reduction through the repurposing of food byproducts. [ABSTRACT FROM AUTHOR]

Herein, cherry flower waste-derived activated carbon (CFAC) with self-doped nitrogen is synthesized as a viable energy storage material for green and sustainable energy solutions. The activated carbon derived in this way is examined as an electric double-layer capacitance (EDLC)-type electrode material and sodium-ion battery (NIB) electrode material, and commendable performance is demonstrated for both of these energy storage applications. The specific surface area (SSA) and nitrogen content are observed to play a very delicate role in determining the charge storage ability of the CFAC, and the performance is optimized only by carefully balancing both of these properties. The optimized CFAC electrode supplied an excellent performance with a specific capacitance of 333.8 F g−1 and capacity is maintained to more than 96% even after 38,000 charge-discharge cycles as an EDLC-type supercapacitor electrode material. Likewise, the CFAC/NIB also yielded remarkable performance with an average specific capacity of 150 mAh g−1 and capacity retention of more than 84% after 200 charge-discharge cycles. Furthermore, an electrokinetic study was performed for both supercapacitor and NIB applications to identify the contribution from surface and diffusion type charge storage phenomena, consequently highlighting the role of the SSA and nitrogen content in the CFAC matrix. [Display omitted] • Scalable synthesis of cherry flower waste-derived activated carbon (CFAC). • CFAC shows a significant amount of self-doped nitrogen and a large SSA. • Applied as an EDLC type supercapacitor and sodium-ion battery electrode material. • 334 F g−1 sp. Capacitance and over 96% capacity retention after 38,000 cycles. • Commendable sodium-ion battery performance with high sp. Capacity and stability. [ABSTRACT FROM AUTHOR]

The rapid rise of the world population increases the annual amount of waste textile products. Textile products create a significant amount of CO2, water, and chemical footprints during production. Therefore, the reusability of textile products has an important environmental and economic impact. Waste denim was used in this study to produce activated carbon (AC) samples as the alternative substance for supercapacitor electrodes. Characterisation studies showed that AC samples contain nitrogen originating from the elastane in the denim structure. Electrochemical characterisation tests proved the pseudocapacitive behaviour of the denim-derived AC due to the nitrogen content. Specific capacitance values observed for the three-electrode and two-electrode cell configurations were 95.93 F/g and 54.64 F/g at 1 A/g, respectively. Good capacitive retention (83.01%) of the cell after 3000 galvanostatic charge-discharge cycles at 1 A/g shows that waste denim can be considered as raw material for energy storage systems. [ABSTRACT FROM AUTHOR]

One of the global problems is environmental pollution by different biowaste. To solve the problem, biowaste must be recycled. Waste-free technology is also a way of saving exhaustible raw materials. Research on electrochemical energy sources is currently the most dynamically developing area of off-grid energy. Electrochemical capacitors can operate for a long time without changing performance, they have smaller dimensions, high mechanical strength, and a wide operating temperature range. These properties are effective energy-saving devices. Therefore, supercapacitors are widely used in various industries. This review discussed the methods of obtaining and the characteristics of biowaste-derived activated carbon and carbon–manganese oxide (AC-MnO2)-based supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

The CoNi-based hydroxide nanosheets (CoNiNSs) are promising active materials for supercapacitors. At the same time, the fabrication of freestanding electrodes is essential to achieve high electrochemical performance without introducing inactive components. To further improve the utilization of electrochemically CoNiNSs, in this study, a nickel-based foam/tube current collector (NF@NT) is rationally fabricated to support CoNiNSs (NF@NT/CoNiNSs). As expected, the freestanding NF@NT/CoNiNSs-2 electrode with optimum CoNiNSs content exhibits favorable electrochemical performance: (i) in the three-electrode system, the specific capacitance is 4.2 F cm−2 at 10 mA cm−2 and 2.38 F cm−2 at 50 mA cm−2, as well as capacitance retention of 97.1 % after 20,000 cycles at 20 mV s−1; (ii) matched with activated carbon (AC), the capacitance of corresponding NF@NT/CoNiNSs-2//AC device maintains 90.74 % after 27,500 cycles at 50 mA cm−2, which also delivers an energy density of 80.8 Wh kg−1 at a comparable power density of 5997.52 W kg−1. • The freestanding NF@NT/CoNiNSs electrode for supercapacitors is fabricated via direct growth of CoNiNSs on NF@NT. • The NF@NT/CoNiNSs electrode endows large contact area with electrolyte, short ion diffusion transport, and fast electron pathway. • The NF@NT/CoNiNSs//AC maintains 90.74 % capacitance after 27,500 cycles at 50 mA cm−2. • The NF@NT/CoNiNSs//AC delivers an energy density of 80.8 Wh kg−1 at a comparable power density of 5997.52 W kg−1. [ABSTRACT FROM AUTHOR]

This study presents the development of green and sustainable supercapacitor electrodes using activated carbons derived from industrial waste from red pepper (RPW) via conventional chemical activation using ZnCl 2 at various carbonization/activation temperatures. The activated carbon samples were subjected to various analytical techniques, including elemental analysis, N 2 adsorption-desorption, Raman, FT-IR, and SEM-EDS. The resulting carbon samples were then used to prepare standard coin-sized supercapacitor cells, which were tested using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques with a 6 M KOH electrolyte. The BET surface area and surface functionality of the samples decreased as the temperature increased. The material produced at the highest temperature (AC800) exhibited the lowest gravimetric capacitance value (131 F/g). However, it demonstrated perfectly reversible electrochemical behavior with the highest capacitance retention of 50 % (between 0.5 A/g and 10 A/g) and cyclic stability (>96 %) over 10,000 cycles among all the other materials. Conversely, the electrode material produced at the lowest temperature (AC600) had the highest gravimetric capacitance value of 175 F/g but the lowest electrochemical stability due to the contribution of pseudo faradaic processes in the storage mechanism. [Display omitted] • Activated carbons (ACs) were derived from RPW with ZnCl 2 at various temperatures. • ACs were examined as supercapacitor electrodes materials. • The temperature had significant impact on the textural properties and capacitive behavior of ACs. • AC600 had the highest gravimetric capacitance thanks to the contribution of pseudo capacitance. • AC800 showed best reversibility, cyclic stability, and capacitance retention as the electrode material. [ABSTRACT FROM AUTHOR]

Developing technological solutions that use yerba mate waste as precursors is key to reducing the environmental impact caused by the lack of treatment and its accumulation in landfills. Due to their physicochemical properties, these residues can be used to develop activated carbons. Activated carbon is a versatile material with a high surface area that can be used for energy storage. In this work, yerba mate residues were valued by producing chemically activated carbon to be used as electrode material in supercapacitors. Activated carbons were developed through chemical activation in two steps with KOH. Variables such as impregnation ratio and activation temperature are studied. The developed carbons were characterized by physicochemical and electrochemical techniques. They were found to have high surface areas, up to 1800 m2 g-1, with a hierarchical porous distribution. A maximum specific capacitance of 644 F g-1 at 0.1 A g-1, and power values of ca 32,000 W kg-1, at 33 A g-1 were found. All the synthesized carbons have excellent electrochemical properties and are suitable for use as active material in supercapacitors. [Display omitted] • Activated carbons are successfully synthesized using yerba mate as a precursor. • The activated carbons have high surface areas and hierarchical pore distribution. • The maximum specific capacitance reach is 644 F g-1 at 0.1 A g-1. • The maximum capacitance retention is 91% at 7.5 A g-1, after 1000 cycles. • The synthesized carbons are suitable as active materials in supercapacitors. [ABSTRACT FROM AUTHOR]

• Strong coupling was established between NiCo-DH and OAC by oxidation modification. • NiCo-DH@OAC exhibited excellent electrochemical performance for synergistic effects. • ASCs were demonstrated effective in solar panel integrated supercapacitors. NiCo double hydroxide (NiCo-DH) and oxidized activated carbon (OAC) were used to synthesize a three-dimensional (3D) NiCo-DH@OAC via hydrothermal method. OAC acts as the support for in-situ growth of NiCo-DH nanowires, and oxygen-containing groups on the surface of OAC are crucial for the uniform loading of NiCo-DH and keeping structural stability of the composites. Due to the synergistic effect between NiCo-DH and OAC, NiCo-DH@OAC presents an excellent specific capacitance (1990 F g−1 at 1 A g−1). The asymmetric supercapacitor (ASC) is assembled with NiCo-DH@OAC as the positive electrode and OAC as the negative electrode, and exhibits a superior energy density (46.5 Wh kg−1 at 800 W kg−1) and a cycling stability (90.7% after 10,000 cycles). Furthermore, ASC has been demonstrated effective in solar panel integrated supercapacitors. [ABSTRACT FROM AUTHOR]

The functional combination of methylene blue and activated carbon successfully introduced a significant redox reaction in the activated carbon, increasing the specific capacitance of the material and significantly improving the rate performance. The methylene blue adsorbed on the surface of activated carbon enables fast proton-coupled electron transfer. [Display omitted] • Anthracite can be activated at low temperature and show large specific surface area. • Oxygen groups could effectively contribute the pseudo-capacitance to AC. • The π-π binding endows AC/MB excellent electrochemical properties. • The optimized AC/MB as positive can deliver ultrahigh energy and power density. • Mathematical simulation can optimize the ratio of positive to negative electrodes. Supercapacitors are desired to deliver high power and energy density concurrently, and the introduction of a redox reaction is an effective strategy to improve their capacitive performance. Herein, methylene blue (MB) with redox was employed to functionalize coal-based activated carbons (ACs) as electrode materials for energy storage. The optimized AC shows a high specific capacitance of 408.1 F g−1 in 6 M KOH, deriving from the contribution of the electrical double-layer capacitance of pores and pseudocapacitance of oxygen groups. Interestingly, pure MB shows no capacitive performance mainly due to its low conductivity, while the optimized composite of AC adsorbed MB (AC/MB) surpasses the pure MB and optimized AC in any capacitive performance, displaying a relationship of mutual promotion based on functional combination. The best AC/MB sample exhibits a high specific capacitance of 431.8 F g−1 at 1 A g−1, and 356.1 F g−1 (82.5%) at an ultrahigh current density of 180 A g−1, implying an excellent rate performance. Aiming to deliver maximum energy density, an accurate universal method is proposed to match the mass ratio of negative to positive. The optimized asymmetric supercapacitor AC/MB(+) || AC(-) delivers an energy density of 11.0 Wh kg−1, a power density up to 15.3 kW kg−1 and a high capacity retention rate of 96.3% after 10,000 cycles, displaying good chemical stability. This work proposes a promising strategy for ultrafast store/release energy at high energy density, and also provides an application direction for AC and MB. [ABSTRACT FROM AUTHOR]

Activated carbons (AC) from lignocellulosic biomass feedstocks are used in a broad range of applications, especially for electrochemical devices such as supercapacitor electrodes. Limited studies of environmental and economic impacts for AC supercapacitor production have been conducted. Thus, this paper evaluated the environmental and economic impacts of AC produced from lignocellulosic biomass for energy-storage purposes. The life cycle assessment (LCA) was employed to quantify the potential environmental impacts associated with AC production via the proposed processes including feedstock establishment, harvest, transport, storage, and in-plant production. A techno-economic model was constructed to analyze the economic feasibility of AC production, which included the processes in the proposed technology, as well as the required facility installation and management. A base case, together with two alternative scenarios of KOH-reuse and steam processes for carbon activation, were evaluated for both environmental and economic impacts, while the uncertainty of the net present value (NPV) of the AC production was examined with seven economic indicators. Our results indicated that overall "in-plant production" process presented the highest environmental impacts. Normalized results of the life-cycle impact assessment showed that the AC production had environmental impacts mainly on the carcinogenics, ecotoxicity, and non-carcinogenics categories. We then further focused on life cycle analysis from raw biomass delivery to plant gate, the results showed that "feedstock establishment" had the most significant environmental impact, ranging from 50.3% to 85.2%. For an activated carbon plant producing 3000 kg AC per day in the base case, the capital cost would be USD 6.66 million, and annual operation cost was found to be USD 15.46 million. The required selling price (RSP) of AC was USD 16.79 per kg, with the discounted payback period (DPB) of 9.98 years. Alternative cases of KOH-reuse and steam processes had GHG emissions of 15.4 kg CO2 eq and 10.2 kg CO2 eq for every 1 kg of activated carbon, respectively. Monte Carlo simulation showed 49.96% of the probability for an investment to be profitable in activated carbon production from lignocellulosic biomass for supercapacitor electrodes. [ABSTRACT FROM AUTHOR]

We developed a continuous-flow three-dimensional electrode reactor (3DER) to remove ibuprofen (IBP) from water. The effects of the operating parameters on the 3DER performance were investigated. The 3DER was constructed by filling a conventional two-dimensional electrode reactor with granular activated carbon, which acted as particle electrodes. The IBP removal efficiency of the 3DER was 98% in 4 h, which was 2.5 times higher than the removal efficiency for the two-dimensional electrode reactor. IBP removal kinetics tests indicated that the current density (1–20 mA/cm2) correlated better than the other operating parameters with the first-order rate constant (k). The flow rate affected the IBP removal kinetics to a small degree. Chloride and sulfate supporting electrolyte concentrations between 17 and 100 mM affected the IBP removal kinetics in opposite ways. Increasing the chloride concentration increased k, but increasing the sulfate concentration decreased k. Radical quenching experiments indicated that much more IBP degradation occurred through both indirect and direct oxidation mechanisms in the 3DER than in the two-dimensional electrode reactor. The particle electrodes caused hydroxyl radicals to form when the 3DER treatment was started, but the particle electrodes later acted as third electrodes and favored direct oxidation of IBP. Image 1 • A continuous-flow 3DER was developed for treating ibuprofen (IBP). • Current density had the greatest influence on the IBP removal rate. • 3DER enhanced both indirect and direct oxidation of IBP compared to 2DER. • Direct oxidation of IBP became dominant as 3DER operation proceeded. [ABSTRACT FROM AUTHOR]

Some recent developments in the preparation of biomass carbon electrodes (CEs) using various biomass residues for application in energy storage devices, such as batteries and supercapacitors, are presented in this work. The application of biomass residues as the primary precursor for the production of CEs has been increasing over the last years due to it being a renewable source with comparably low processing cost, providing prerequisites for a process that is economically and technically sustainable. Electrochemical energy storage technology is key to the sustainable development of autonomous and wearable electronic devices. This article highlights the application of various types of biomass in the production of CEs by using different types of pyrolysis and experimental conditions and denotes some possible effects on their final characteristics. An overview is provided on the use of different biomass types for the synthesis of CEs with efficient electrochemical properties for batteries and supercapacitors. This review showed that, from different biomass residues, it is possible to obtain CEs with different electrochemical properties and that they can be successfully applied in high-performance batteries and supercapacitors. As the research and development of producing CEs still faces a gap by linking the type and composition of biomass residues with the carbon electrodes' electrochemical performances in supercapacitor and battery applications, this work tries to diminish this gap. Physical and chemical characteristics of the CEs, such as porosity, chemical composition, and surface functionalities, are reflected in the electrochemical performances. It is expected that this review not only provides the reader with a good overview of using various biomass residues in the energy storage applications, but also highlights some goals and challenges remaining in the future research and development of this topic. [ABSTRACT FROM AUTHOR]